Plug-in contact and blast valve unit

ABSTRACT

A plug-in main contact and blast valve unit is inserted or withdrawn through the end of a housing or tank of a gas-insulated substation arrangement. Conducting self-aligning ring and compensating securing means adjust for angular and linear tolerance variations. Bolting means between the contact housing, elbow, and header include an adjustable seating sleeve on each side of the elbow for positioning the contact and valve unit for both horizontal and vertical adjusting movement in the tank to obtain the necessary mechanical and electrical clearances. Special guides and tapering arrangements facilitate the alignment procedure and sealing arrangement. A service unit is provided to facilitate a guiding and positioning insertion and withdrawal of the contact and blast valve unit into and out of the tank.

United States Patent 1 1 Goodwin, Jr, 1

[ Dec. 3, 1 974 PLUG-IN CONTACT AND BLAST VALVE A Primary Examiner-Robert S. Macon UNIT Attorney, Agent, or Firm-Robert C. Jones [7 5] Inventor: Edwin C. Goodwin, Jr., Canton, 7

I Mass, 57] ABSTRACT [73] Assignee: Allischahfiers Corporation A plug-in main contact and blast valve unit is inserted Milwaukee Wis or withdrawn through the end of a housing or tank of i a a gas-insulated substation arrangement. Conducting Flledl y 8 3 self-aligning ring and compensating securing means [21] Appl 380,248 adjust for angular and linear tolerance variations. Bolting means between the contact housing, elbow, and header include an adjustable seating sleeve on [52] US. Cl 200/148 R each side f the dim, f positionin he Contact and g CL 1 valve un t for honzontal and erti al adju ting [58] Field of Search 200/148 R, 148 B, 145 R movement in the tank to obtain the necessary chanical and electrical clearances. Special guides and 1 References clted I tapering arrangements facilitate the alignment proce- UNITED STATES PATENTS dure and sealing arrangement. A service unit is pro- 3,o07,021 10/1961 Prunty et al. 200/145 R Vided to facilitate a guiding and Positioning insertion 3,214,546 10/1965 Leeds 200/145 R and withdrawal of the contact and blast valve unit into 3,278,712 10/1966 Tominaga ZOO/148 R and out Of the tank. 3,555,227 1 1971 C 't'l. ..2OO 148 B a I romer c d I 20 Claims, 12 Drawing Figures v a A 73 I m i O I I! I m1 nr, 6,? 64 61 449 '1 1 )1 *j I IILJW l 4 4a t 7 v 66 2M 67 71 r: [i J, 63 (J1 Ts I? (IO h \,d 69 7 .1 \\\\K \\\\\V 5 L I, 4 I

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PATENIEL nan [31914 SHEET '5 0f 7 PATENTEL BEE SHEET 60$ 7 PLUG-IN CONTACT AND BLAST VALVE UNIT SUMMARY OF THE INVENTION This invention relates to substation electrical structures such as a high voltage, gas-insulated circuit breaker for both indoor and outdoor use.

Present known devices are extremely difficult to service and require extensive dismantling of the unit in order to perform the necessary servicing of the circuit insulated circuit breaker constructed and arranged to have a unitized contact, gas blast valve and mechanism assembly which simplifiesmanufacturing, assembling and servicing. I

I A gas-insulated circuit breaker in accordance with the present invention comprises an enclosed gas filled tank or housing atrelatively low pressure having a centrally located source of insulating gas at relatively high pressure, said gas is utilized both as an insulating medium and also as an interrupting medium. The source of gas at relatively high pressure, is directed to 'a centrally. located distribution housing orcasting which serves as a gas flow directing member to a gas valve device. The gas blast valve deviceas well as the interrupting contacts and mechanism are deployed in single component arrangement that can be inserted or withdrawn from the central distribution housing externally I from the ends of thetank. The arrangement eliminates the necessity of dismantling'the tank and its internal elements' when servicing is found necessary and also eliminates the necessity of having. service personnel enter the tank to dismantle or service the breaker or blast valve unit. Insertion of the-contact and blasat valve unit into the distribution casting in gas sealed relationship is facilitated by the provision of a female tapered end which'mates with a male outlet construction that includes a sealingring inthe distribution casting. Belting means secure the "contact and-blast valve unit at its lower end tothe distribution casting and are located so as to effectively resist the large forces exerted by the high pressure gas. Bolting means at the ,top consist of self-alignmng locating and conducting pads which compensate for angular and linear tolerance variations. All securing devices are accessible by service personnel fromthe exterior of the tank. Actuating mechanism associated with the main contact and blast valve permit precise external adjustment and synchronization of contact and valve operation before insertion into the tank. Guided insertion and withdrawal of the contact and blast valve unit into and out of operating position is easily accomplished by means of a lightweight dual rail device which facilitates handling of the relatively heavy contact and blast valve unit.

DESCRIPTION OF THE DRAWINGS I FIG. 1 is a view in elevation of a substation circuit breaker installation utilizing a plurality of series related gas-insulated circuit breakers in which the present invention is incorporated;

FIG. 2 is a plan view of one phase of the substation circuit breaker arrangement shown in .FIG. 1 FIG. 3 is an enlarged fragmentary detailed view of the control portion of one of the gas-insulated circuit breakers showing one of the main contacts and its associated blast valve in operating association with the central high pressure gas distribution housing;

FIG. 4 is a view similar to FIG. 3 showing the circuit vbreaker main contact and blast valve unit separated from the central high pressure gas distribution housing and upper support;

FIG. 5 is an enlarged detailed view in horizontal section taken in a plane represented by the line V-V in FIG. 3 showing an adjustable conducting and mounting FIG. 6 is an enlarged detailed view in horizontal section taken in a. plane represented by the line VIVI in FIG. 3 showing the arrangement of an adjustable seating sleeve and associatedlocking bolt for positioning the contact and valve unit both horizontally and vertically; a T-wrench being illustrated for tightening or loosening the belt from the exterior of the tank, with an adaptor for adjusting the seating sleeve;

' FIG. 7 is a ,view partly in horizontal section and partly in plan through one end of a circuit breaker tank showing the service unit in position for contact. and blast valve unit; FIG. 8 is a view partly in vertical section and partly in elevation showing the service unit'arrangement depicted in FIG. 7, the contact and blast valve unit being shown in broken lines asit would appear when" withdrawn from the tank;

FIG. 9 is a view partly in horizontal section and partly in plan-similar to'FIG. 7 with the service unit arranged for insertingthe contact and blast valve unit'into operating position within the tank;

FIG. 10 is a view partly in vertical section and partly in elevation showing the service unit arranged for insertion with the insertion mechanism fully extended after completing the operation of inserting the-contact and blast .valve 'unit into operating position;

FIG. 1 lis a view in elevation of the contact and blast valve housing the glass flow passages and the threepoint support arrangement; and,

FIG. l2-is an. enlarged fragmentary detailed view of contact .and blast valve unit of FIG. 3 modified to ac-,

commodate a vsingle interrupter arrangement for minimal interrupting capacity. I

DESCRIPTION OF THE INVENTION Referring now to the drawings, and more particularly to FIGS. 1 and 2 thereof, there is depicted a substation installation 20 comprising a plurality of series connected gas-insulated circuitbreakers 21, 22 and 23. Each circuit breakeris substantially identical; and thus, a description of the circuit breaker22 will also apply to the breakers 21 and 23. The circuit breaker 22 includes a pair of contact and gas blast valve units 26 and 27 which are electrically connected in series through a centrally located support housing or casting 28. The contact and gas blast valve units 26 and 27 as well aswithdrawing the the centrally disposed support housing 28lare disposed within a gas-tight tank 31 having an insulating gas at relativey low pressure therein. Synchronouos operation of the movable main contact 32, FIG. 3, and of the gas blast valve 33 of the unit 26 is effected by operating linkage 35.

Gas at a relativey high pressure is contained within a supply tank 36 which is secured in gas-tight relationship to a depending mounting flange 37 integrally formed with the bottom of the tank 31.. A supply of gas from the supply tank 36 is directed to the central distribution header 104 by means of a supply pipe 38 which has gas-tight fitting relationship with the header 104 and the tank'36.

Support for both contact and valve units 26 and 27- as well as for the relatively heavy central support con sisting of housing 28, support 28A and header 104, and the associated operating linkage 35 and the identical operating linkage (not shown) associated with the contact and valve unit 27 is afforded by means of a downwardly extending internal insulator housing or' tion of the mechanism 57 upon a proper signal from a source (not shown) will cause the mechanism to operate in one direction to effect the opening of the contacts and valves. On the other hand, operation of the mechanism 57 in the opposite direction, in accordance with the proper signal, will effect the closing of the contacts.

As previously mentioned, the contact and blast valve units 26 and 27 are constructed and arranged for guided insertion and withdrawal from the tank 31 through an adjacent service end of the tank; Contact and blast valve unit 26 is shown in FIGS. 3 and 4, and a description of this unit will also apply to the unit 27. As shown, the unit 26 comprises an insulator contact tube or casing 61 in which a fixed contact support tube 62 is disposed. Resilient inwardly biased contact fingers 63 are supported in the right end of the tubular support 62. Surroundingthe resilient contact fingers 63 is a gas flow deflector 64.Supported for axial movement into and out of engagementwith the resilient contact fingers 63 is the movable tubular contact 32 that is supported by a fixed nose piece 67 containingtransfer .contactfingers 63A. The nosepiece 67 is secured'to the extending end of a tubular projection 68 integrally formed with a main contact housing 69. For supporting the main movable contact 32 for guided axial reciprocation in the. tu-

blast andoth'er vibrational effects on the support housing 28 the insulated high pressure gas feed pipe operates through parts 104 and 28A to-impart a stabilizing effect'to the housing 28. I

As previously mentioned, operation of the movable contact 32 and opening of the blast valve 33 of the contact and valveunit 26 as well as the identical counterparts (not shown) associated with the contact and valve unit 27 is accomplished through the operating linkage 35 and identical operating linkage (not shown) associatedwith the unit 27. These linkages are actuated by means of a common actuating rod 46 supported for -reciprocal movement in the pipe 39. As shown, the

lower end of the rod 46 is pivotally connectedto a pair of tielinks 47 and 48. The link.47 has an operative connection to the linkage 35 while the link 48 is operatively connected to the linkage (not shown) associated with the unit 27. As viewed in FIG. 3, upward movement of the rod 46 will effect opening movement of the 'movable contacts and the blast valves assocaited with the units 26 and 27. This movement is imparted to the rod 46 .by-rotation of an operating shaft 49 which'is connected through suitablelinkage 51 to the upper end of the rod 46. As shown in FIGS. 1 and 2, the operating shaft 49 is rotated 'by 'a'conne'cting rod and lever system' 49A extending across the top of the three circuit breakers 21, 22 and 23 within a protective housing or tube- 52. At the left end of the phase 20; as viewed in FIGS. 1 and 2, the connecting rod system 49A terminates in a direction change box 53 in which is an operative con-' nection with avertical shaft 54. The vertical shaft 54 bular projection 68 a circular guide 71 is integrally formed around the contact at the right end thereof. Pivotally attached to the right end of the'tubular movable contact 32 is a rod 72 which has its opposite end connected to the contact operating linkage 35. A corona shield 73 surrounds the right end of the contact insulator housing 61. A similar corona shield (not shown) surrounds the extreme left 'end'of the contact insulator housing 61. I 7

In order to more effectively provide the contacts of unit 26 with an'adequate supply of high pressure gas at the area of arcing vat the occurrence of contact separation, an efficient gas valve and flow directing arrangement isprovided. To this'end an elbow housing 76 is provided in which the blast valve 33 is operatively carried. As shown in FIG. 3, the blast valve 33 is secured to the downwardly facing bottom plate 77 formed on the main contact housing'69. The bottom flange 77 of main contact housing is provided with an opening 78 which communicates with asemicircular or horseshoe configured gas passage 79.. Communication between.

the opening 78 and the horseshoe configuredpassage tion 68. Thus, when the valve 33 is displaced from the valve seat 33A, gas at a relatively high pressure will flow through sealing plate 77A into the transverse passage 7 8 and thence into'the horseshoe configured passage 79. The horseshoe configured passage 79 operates to change the direction of flow ofthe gas where it is directed into the communicating circular passage 81. Since the gas flowing inthe horseshoe configured passage 79 is at a relatively high pressure'and its'directio'n of flow is being changed by the passage 79, turbulence in the flow may occur. Thus, the multi-passageddirector 82 serves to straighten the flow of the gas to remove turbulence, thereby retaining the high velocity of the gas flow.

To open the valve 33 is sequencial,synchronization with the opening movement of the contact 32, advantage is taken of the proximity of the contact operating linkage 35 and the offset close coupled arrangement of the valve 33 with respect to the contacts 32 and 63. To this end, the bottom flange 77 of the main contact housing 69 is provided with an opening 86 through which an actuating rod 87 extends. A bushing 88 provides an ovally-contouredguide hole which accepts the chordal displacement of rod 87. At its inner or upper end the rod 87 is pivotally connected to an arm of a rocker 89 which is pivotally secured between spaced apart lugs 91, one of which is shown. The opposite arm of the rocker 89 is pivotally connected to a rod 92 which, in turn, is pivotally connected to a member of the operating linkage 35. To maintain the actuating rod 87 clear of the valve 33 so that a valve closing spring 93 is' freely operative to return the valve 33to a closed position, one end of a rocker spring 94 is attached to the arm of the rocker 8 9 with the opposite end of the spring 94 being attached to afixed stud 96. Thus, the spring 94 operates to exert a constant bias on the rocker 89 for urging it in a clockwise direction, as viewed in FIG. 3, thereby lifting the rod 87-free of the valve 33.

As previously indicated, the contact and blast valve unit 26 is a plug-in unit which can be inserted into operatir'ig position or withdrawn from the ends of the tank 31. To this purpose thelower right end 101 of the valve elbow 76 is formed with a circular tapered leading edge 102. The circular leading edge 102 of the elbow mates with a circular outlet portion 103 of a T-shaped gas distribution header 104. Header 104 operates to receive the gas from. the supply pipe 38 and to direct the gas leftwardly and rightwardly to both of .the contact and blast valve units'26 and 27. Asshown, an O-ring 106 is engaged on the external surface of the header outlet portion 103 and serves'to seal the joint space therebetween.q Z

For guiding and controlling the position of the circular tapered leading edge of the valve elbow 76 as it is moved inwardly to engage on the outlet portion 103 ofthe T header 104 there is provided a positioning guide 107. The positioning guide 1 07 is herein shown as a stud threadedly engaged in a horizontally extending ear portion 108 formed integrally with the base flange 'of the T-header 104. The extending end of the guide stud is formed with a ball 109 on which the elbow will engage and slide. By adjusting the axial position of the guide stud 107, the'elevation at which the circular tapered leading edge 101 of the elbow 76 approaches the circularoutlet portion 193 of the T-headei' can be established.

For securing'the contact and blast valve unit 26 in good conducting engagement with the' central housing member 28, a unique conducting and tolerance equalizing means 110 is provided. As shown in FIGS. 3, 4 and 5, the main contact housing 69 is provided with a projecting pad member 111. Theforward face 112 of the pad member- 111 is machined to provide for good electrical contact against an adjacent conducting and support means'114 provided on the central housing member 28. Since in manufacturing components such as the main contact housing 69 and the central housing 28 tolerance variations are likely to occur, the conducting and support means 114 is self-adjusting to compensate for such tolerance variations and to make good conducting contact with. the face 112 of pad 111. To this end, as shown in FIG. 5, the member 114 is formed as an adjustable pad or washer 116 having a semispherical rear surface 117 which seats within a complementary cavity 118 formed in the central housing member 28. For maintaining the adjustable conducting washer 116 in position, a bolt 119 is employed'The bolt 119 extends through a suitable opening in the washer 116 and a complementary opening in the wall of the central housing member 28. A compression spring 121 is engaged on the threaded end of the bolt 119 and abuts the inner surface of the central member 28 and a nut 122 on the bolt 119. By adjusting the nut 122 on the bolt 119 the spring 121 will apply a desired amount of force to the bolt to maintain the pad or washer 116 adjustably seated within the cavity 118.

Thus, with insertion of the contact and blast valve unit 26 into operating position, the tapered circular edge 102 of the elbow 76 will engage on the circular 104 being guided thereon by the guidesupport 107. With engagement effected betweenthe elbow 76 and the outlet 103 of the gas supply header 104 the conducting pad 111 will engage the adjustable conducting washer 116 to establish the main electrical conducting path between the central housing 28 and the contact and blast valve unit 26. Thus, the elbow 76, passage 79 of main casting 69 and'gas flow chamber 81 define an offset gas flow. channel between the distribution supply header 104 and the area of arcing.

To secure the contact and blast valve unit 26.. in operative position, the elbow 76 is removably fastened to the T-shaped gas supply header 104. To this end, as depicted in FIGS. 3', 4 and 6, the elbow 76 is provided witha pair of laterally extending ears 126 (see FIG. 11), one being indicated by broken lines in FIGS. 3 and 4. The ears 126 are formed integrally with the elbow structure being spaced on eitherside thereof. A bolt 127 extends through a suitable opening inthe ear 126 and threadedly engages in a threaded blind bore 128 provided in a laterally extending flange. 129 formed on theheader 104. It will be understood that the gas supply header 104 is provided with two vbolt receiving flanges, one on each side, with the far side flange 129 being depicted by broken linesin the drawings.

An elbow securing arrangement is shownin detail in 9 FIG. 6. As there shown the lateral extending ear 126 is provided with a threaded bore 131 which receives a threaded axially adjustable stop sleeve 132. The stop sleeve 132 operates to establish the amount of interengagement that will be established betweenthe elbow and the outlet 103 of the header 104. Thus, the sleeves .operate to establish the desired orientation of the contact and blast valve unit 26 with respect to the tank 31, the central housing member 28 and the gas supply header 104. For adjusting the stop sleeve 132 axially within the bore 131 the end of the stop sleeve is provided with a slot 133 in which a snap-in tool 141A-can engage to effect the desired axial adjustments thereof.

The stop-sleeve 132 is provided with an axial bore 134 v 136 is provided to receive a bearing washer 137 against which the head 138 of the bolt 127 engages.

Since the locations of the bolts-127i are not conveniently accessible from. the end of the tank 31, a long handle wrench 139 is provided for engaging or disengaging the bolts 127 and the sleeves 132. As shown in FIG. 6, the wrench 129 isprovided with a head portion v in a peripheral annular. groove formed on the bolt head 138. With this arrangement the possibility of a bolt or tool, such as the bolt 127, being accidentally dropped into the interior of the tank is eliminated. The importance of securing'the bolt 127 or tool to the wrench 139 ismore apparent when it is considered what trouble and cost is entailed should a bolt he accidentally dropped into the tank 31, especially in the area ofthe high pressure tank. If a bolt is accidentally dropped,-it must berecovered before-the circuit breaker can be put into operation. Thus, to recover a bolt either'the circuit breakermust be removedto allow service personnel to crawl into the tank 31 or the high pressure tank 36 must be'removed. In either case, a loss of time with the accompanying cost is experienced.

1 With the contact and blast valve unit 26 secured to the gas supply header 104, the upper po'rtion of the unit 26 is secured to the central housing or member 28. To this end the contact pad 111 is provided with laterally extending flanges 1'46 and 146A as shown in FIG. 5.

Each flange is provided with a pair of vertically spaced bolt passages or slots- 147, 147A and 148, '148A through which securing bolts 149 extend. The bolts engage in suitable aligned threaded bores formed in a boss 150formed on the central housing 28.. Thus, linear tolerance variation in the contact pad 111 will be commpensated for by the vertical slot openings.- ln tightening the bolts 149, the face surface 1120f the contact pad 111 will engage the adjustable washer 116 and thewasher willadjustwithin the cavity 118 to accommodate for angulartolerance variation andtoinsure good electrical contact therebetween. A bolt 149 if accidentallyfdropped into the tank 31 .willbe extremelyidifficult to recover. To do so will entail removal of the contact and blastvalve unit 26 so that a se'rviceman can crawl into the tank." T preventaccidental displacement of a bolt 1 49 from out of an associated slot 147,, 147A, 148 and 148A, there is provided capturing means for returning a bolt to the slot. To this end, as shownin'FlG. 5, each bolt is provided with'a washer 151 which is larger 'i'ndiameter than-the width of the slot 147 through which'it extends. Engaged on the shank of the bolt 149 anddisposed between the wahser 151 and the threaded end of the bolt is a re-v 1 onthe other hand effectively preventsthe O-ring 152 from passing through the slot. Thus, the bolts 149 are effectively captured within their respective slots. Access to the bolts 149 from the exterior of the tank 31 for engaging or disengaging them into or out of securing relationship is afforded by means of sealed ports 153 and 153A both of which have removable sealing covers 154 and 154A.

As mentioned, it is necessary to assemble and service the contact and blast valve unit 26 exterio'rly of the tank 31. To facilitate the insertion and withdrawal of the contact and blast valve unit-26 into and out of the tank 31 through'the end of the tank with a minimum of manpower and space at the tank end, a service unit 155 is provided. As shown in FIGS. 2, 7 8, 9 and 10, the

service unit 155 is provided with a pair of spaced external cantilever guide rail supports 156and 156A. The

cantilever supports 156 and 156A are deniountably attached to the lower ends of associated vertical angle members 157 and 157A. The angle members 157 and 157A areremovably bolted to the tank end door flange 158. A- pair of horizontally spaced rail members 159 and 159A have their inner or tank ends bolted to suport blocks 161 and 161A carried by the vertical angle members 157 and 157A, respectively. The outboard ends of the rails 159 and 159A are bolted to the cantilever supportrail supports- 156 and 156A.-Within the tank 31 there is an auxiliary pair of spaced guide members 162 and 162A which constitute extension of the outboard rails 159 and159A, respectively. For opera- .tively supporting the inboard r'ails162 and 162A within the rails 162 and 162A, as viewed in FIGS. 7, 8, 9 and 10, are bolted to the support blocks 161 'and'161A re-.

spectively. As depicted in F IGS. 7, 8, 9 and 10, themboard rails 162 and 162A in operative position are disposed below-horizontal lateral projections 166, 166A and 167, 167A-provided on each side of the corona shields 73 .and 73A, respectively. Thus, 1. with. the contact and blastvalveunit 26 released] from thecentral housing member 28" andheader 104 the unit26tis carried on the rails 1162 and 162A. 1

- For withdrawing-the contact and blast valve unit 26 from the tank 3 1,.a' winch device-168, as shownin FIGS 7 and,8,'jis provided. The winch devicev168fis mounted at the extreme outerendsiof the outboard rails'159 and1-59Aon a horizontalcross member 169 which ties-the spacedrail members together. For withdrawing the contact and blast va'lve unit 26 out'of the tank 31 along-the rails the winch device 168includes a worm and worm wheel drive 171 that is car'riedin a bracket 172 mountedonthe cross-member 1 69. A drum 173 mounted in coaxial relationship torotate with the worm wheel member of the winch hasa wire rope 174 connected thereto. The wire rope 174 travels over a horizontal idler pulley 176 which is mounted for rotation on the cross member 169. The free .end of the wire rope 174 is provided with an attachingmeans such as-a hook 177 by which it is releasably connected to the end of the contact and. blast valve unit 26. Rotation of the drum g73 peration. of a hand crank 179 will wind; th'e ro cause the urifastened contact andblast valve unit 26 to move along the rails-from the position it occupies, as

1 74 'on ithe drum 173. This will depicted in .full lines, to a position outside of the tank 31,-as depicted by broken lines'in'FIG. 8. By establishing the rails on anincline plane, the contact and blast valve unit 26,-asiit1m'oves along the rails, is gradualty moved upwardly so that the bottom curved surface of pushing it along the railsel-iowever, the further the unit 26 is moved along the rails into the tank 31 the more difficult it becomes to exert the degree of leverage necessary to keep the unit moving. Also, the engagement of the elbow 76 on the outlet 103 of the gas supply header 104 requires an additional force to effect a sealing mating engagement with the O-ring 106. To provide the additional force that is required, aninsertin'g toggle device 185 is provided, as shown in FIGS. 9 and 10. As there shown, the toggle device 185 comprises a breakit may be removed After the insertion of the contact and blast valve unit 26 into itsoperating position has been accomplished the toggle device 185 is disconnected from the unit 26 and dismantled from the service unit 155. The service able frame including a rightwardly disposed V-shaped thrust member 186. The bifurcated left end of the thrust member 186 is pivotally mounted on a bar memher 187 which also pivotally receives the forward or rightwardly disposed ends of a base member 188. The rear or left end of the base member 188, as viewed in FIGS. 9 and 10, are pivotally connected to a horizontal bar 189 that is removably disposed within .aligned openings formed in the sides of the rails 159 and1S9A.- A quick release connection arrangement is provided on the forward end of the thrust member 186 to simplify the disengagement of the toggle device 185 from the contact and'blast valve unit 26 after it has been moved into operative position. To this end'the forward end of the thrust member 186 is formed with'a downwardly inclined slot 191 'which is adapted to engage on a pin 192 carried in a pair of spaced projections or lugs 193 I provided on the contact and blast valve unit 26.

' device will bebroken with the mid portion including the bar-187 being in an elevated position. The operator will apply a downwardly acting force to the. bar .187 to collapse the toggle device-155 forcing the contact and blast valve unit 26in a guided path of travel'al'ong the downwardly inclined inner rails 162-162Ainto its operating position. As the contact and'blast valve unit 26 moves into its operating position the approach elevation of the tapered inlet 102 relative to the outlet open ing 103 will be guidably established by the positioning guide 109, FIGS. 3 and 4, so that positive sealed mating engagement is effected.

unit 155 is then unbolted from thedoorflange 158 of the tank Bland removed. The hinged door, FIG. 2, is closed and secured. v v

In FIG. 12 the circuit breaker has been illustrated as it would be modified for a particular installation reqiiiring minimal initial interrupting capacity but which be readily and inexpensively expanded at a future time; I

To this end, the rightwardly disposed gas supply buti let 196, as viewed in Pro. 12, is blocked by a cap 197.

The cap 197 is secured over the header outlet 196-by means of screws (not shown) which register in suitable openings provided in flanges 198. The flanges 198 are identical to the flanges 129 to which the elbow 76 is secured.

' For effecting continuity in the electrical circuit from the interrupter unit 26 via the central housing 28, there is provided a conductor 199. The conductor 199 is provided with a contact pad 201 similar to the pad 111 associated with the interrupter unit 26. Screws 203 inserted through the pad 201 threadedly engage in the mounting abutment 204 to secure the conductor contact pad 201 in good electrical contact with an adjustable washer 206. The opposite end of the conductor 199 (not shown) is operatively connected'to the bottom of the bushing stud suchas the bushing 208 depicted in FIG. 1.

The modified arrangement of FIG. 12 provides great flexibility and also provides economies to the purchaser allowing him to install units of minimal interrupting ca- I pacity and thereafter to expand the interrupting capac-' ity as required.

The embodiment of the invention in which an exclu sive property or pivilege' is claimed are defined as followsz" V I 5 1. In a gas-insulated circuit breaker: a circuit breaker tank having a service opening; a contact and blast valve unit inse'rtable through the service opening in said tank into operative position in said tank; I v a gas supply distribution member supported within the interior of said tank; an outlet formed'on ,said distribution member;

' a tapered inlet formed in said contact and blast valve unit to cooperate with said outlet of said distribution member; and, an O-ring carried by said outlet for effecting a gas tight seal b etween said outlet and'inlet when mating engagement is: effected between said inlet and outlet upon insertion of said contact an'djblastvalve unit intooperating position within-said tank. g 2. A gas-insulated circuit breaker according toclaim 1 wherein there is provided guide means to guide said ing position-in said tank. 3.111 a" circuit breaker: a'tankg" asupport housing carried by said tank in the interior thereof;

' a contact andblast valve unit having afastening block for securement to said support housing, 'said fastening block also serving as an electrical concontact and blast valve unit as it is'in'serted into operata conducting self-adjusting ring carried by said support member in position to be engaged by said fastening block when said contact and blast valve unit 12 tion relative to the complementary outlet portion of said distribution means so that mating engagement between the complementary inlet and outlet portions will occur. as said contact and blast valve unit is inserted into operative position in said tank.

is inserted into operative position within said tank. g

I 7. A gas-insulated circuit breaker. according to claim 4. A circuit breaker according to claim 3 wherein 6 wherein the complementary inlet and outlet portions said fastening block is provided with a slotted opening are of annular configuration and one of said portions is through which fasteners are inserted to engage in said 10 provided with an annular tapered edge for facilitating support housing; and, the mating engagement between said portion.

capturing means associated with said fasteners and 8. A gas-insulated circuit breaker according to clain cooperable with said fastening block to retain said 6 wherein said guide means is a ball guide supported for bolts within said slots when said fasteners are .not axial adjustment and in position to engage the bottom engaged in said support housing; surface of said contact and blast valve unit as said unit whereby said fasteners are readily accessible for enis moved into operative position within the tank.

gagement in said support housing and are pre- 9. A gas-insulated circuit breaker according to claim vented from accidental dislodgment from said slots 6 wherein one of said portions carries a seal operable when not engaged. to seal the joint space between said complementary 5. in a circuit breaker: inlet and outlet portions when mating engagem en a tank; v therebetween is effected. p

a support housing within said tank; 10.. In a gas-insulated circuit breaker:

a contact-and blast valve unit comprising an insulator a circuit breaker tank havinga service opening;

housing in which a fixed main contact is located;

a main contacthousing-having a movable contact support projection in which a movable main contact is disposed for axial movement, said support projection extending into said insulatorhousing in annularly spaced'relationship to thereby define'an annular gas passage; v

an annular gas passageway formed in said main tion therein, said contact and blast valve unit. having a gas inlet; a gas supply distribution member supported within said tank and having an outlet complementary to the inlet of said contact and blast valve unit for mating engagement with said outlet; and,

a contact and blast valve'unit insertable through the service opening in said tank into an operative posicontact housing around said projection in position to communicate with the vannulargas passage formed between said projection and the interior'of ing a gas inlet portion; v

a gas supply distribution means supported within said tank, said distribution means having an outlet portion complementary to said gas inlet portion of said contact and blast valve unit; .and

I 65 guide meansoperable to control the elevation-of the guide means operable to control the lateral direction and the elevation of said contact and blast valve .unit to establish'substantial alignment ofsaid inlet said contact housing; relative -to said outlet so that mating engagement gas supply passage formed in said main contact between said inlet and outlet will occur as said housing in communication with said annular pascontact and blast valve unit .is inserted intooperatsage formed in said main contact housing, said gas ing position withinsaid tank; supply passage also communicating with the'end of 11. in combination: said main contact housing; Y 40 a circuit breaker tank having'a service opening; hollow elbow secured to the end of said main a support member carried by said tankwithin the incontact housing and having communication with terior thereof; said gas supply. passage, the opposite end of said a contact and blast valve unit'removably attached at elbow forming a gas inlet, the axisof which is subone end to said support member; t stantially parallel to the axis of said insulator housan interior rail support extending between said'suping; I v I port member and the service opening, saidinterior gas supply distribution member within said tank, railsupport having its innerend restably confined said distribution member having an outlet which i on said support member, theouter end of said intemates in sealed relationship with the inlet of said rior railsupport being detachably supported by elbow; and, j j j said tank at a position adjacent the service opening valve within said elbow normally operable to seal, and at an elevation above the level at which the thecomrnunication connection between saidelbow inner end of the rail support is supported; andsaid gas supply passage in said main contact an exterior rail support detachably secured in cantileousin ,v I I i ver relationship to said tar ik,"said 'exterior railsup- 6. ln agas-insulated circuit breaker:- port extending away from the opening in said tank a circuit breaker tank having a service opening; to provide an external support for a contact and a contact and blast valve unit insertable through the blast valve unit, said exterior railsupportbeing in 5 service opening in said tank into an operative posialignment with said, interior rail support and having tion therein, said contact and blast valve unit havthe same gradeas said interior rail support; and,

a breakable A-frame member having one 'leg releasably attached to said exterior railsupport'and'its opposite leg-releasably connected to said contact and blast valveunitj whereby collapsing of ,,said ,A frame impels jsaid contact. and blast. valve unit along said rails supports and into operating engagement with saidsupport member.

12. In a gas Circuit breaker: casing means defining an arcing chamber and having is communicating gasflow directing annular orifice portion for directing gas under pressure to said arcing chamber; a stationary contact structure having a gas exhaust opening associated therewith extending within said casing means;

a movable tubular contact havinga gas exhaust opening therethrough and cooperable with said stationary contact structure in said arcing chamber of said casing means; y means defining a gas receiving chamber surrounding said movable contact in communication with said gas flow annular orifice portion of said casing means, I a pressurized gas chamber angularly offset relative to said gas receiving chamber surrounding said movable contact and having gas under pressure therein;

a gas supply passage between said pressure gas chamber and said gas receiving chamber; and,

valve means in said pressurized gas chamber normally operable to seal the opening between said gas supply passage and saidpressure gas chamber. 13. A gas circuit breaker according to claim 12 wherein said casing is providedwith a pocket'rearwardly of the gas exhaust opening of said movable contact; and, I

means operable supported in said pocket out of the direct path of said gas exhaust opening of said movable contact for actuating said valve to open position 'to allow pressure gas to flowfrom said pressure gas chamber into saidcommunicating'gas supply passage. v 1 14. A gas circuitbreaker according to claim 13 wherein'there is provided operating means connected to effect synchronized openingrnovment of said movable contact and operation of saidvalve actuating i whereby pressure gasis directed to said arcing cham-' means being engageablein said support housing to v secure the bottom portion ofjcontact andblast valve unit to said support; I I whereby said contact and blast vlave unit is secured in operative position within said tank with three point suspension. l a 16'. Agas blast circuit breaker according to claim 15. wherein: Q' i 3 t said single upper support bracket is a main electrical conducting member; I

' said support housing ispro'vided withaf selfiadjusting electrical conducting washer adapted'tobe en gaged by said upper sup port; bracket;

said spaced apart lower securing means each include an axially adjustable sleeve having a bore operag a contact and blast valve unitsupported in operative tively carried by the lower portion of said contact and blast valve unit; and,

a bolt extending through the axial bore in said adjustable sleeve into threaded engagement with said support housing, said bolt having abutment means engageable with said contact and blast valve unit but does not engage said sleeve, said bolts operating to secure the bottom portion of said contact and blast valve unit but does not engage said sleeve, said bolts operating to secure the bottom portion of said contact and blast valve unit to said support housing and also to lock an associated sleeve in an adjusted position;

whereby each sleeve of said lower securing means can be adjusted individually to adjust the position of said contact and blat valve unit within said tank and said self-adjusting washer compensates for angular variation. I

17. In a gas blast circuit having:

a tank; and,

a contact and blast valve unit operatively disposed within said tank, said contact and blast valve unit comprising: i

a casing defining an arcing chamber and into which gas under pressure is to be supplied; J

a fixed tubular contact in said casing with the bore thereof operating as an exhaust passage to vent a portion of the gas supplied to said arcing chamber to said tank; 7

a movable tubular contact supported within said arcing chamber in coaxial cooperating relationship to said fixed contact, the bore of said movable contact operating as an-exhaust passage;

a source of gas under pressure;

a pressure gas chambe'r'connected to receive gas under pressure from saidsource; v 1

an annular gas directing chamber surrounding said movable contact to direct gas under pressure to said arcing chamber, said annular gas directing chamber defining a gas exhaust passage into which the bore of said tubular movable contact vents in.

- a straight line path; i

a gas'flow passage in communication with said annular gas" directing chamber but angularly offset I therefrom; said gas flow passage also having comj munication with said pressure'gas chamber;

means normally operable to block the flow of gas under pressure from said pressure gas chamber to said gas flow passage; and, i r

\ means for actuating said blocking means from-its nor- 'tially offset from the direct line of exhaust gas flow.

l8; iln a gas-insulated circuit breaker:

a circuit breakerv tank; a H

a gas supply tank supported-by said'circuit breaker tank;

a gas supply distribution member in communication with said gas supply t-ank, said *gassupply distribution-member having at least one outlet;

position within said tank;

an offset gas flow channel between said distribution member and an arcing area, the end of said offset gas flow channel adjacent said distribution member defining an inlet constructed and arranged to cooperate with the outlet presented by said distribution member, the arrangement being such that said inlet and outlet cooperate to effect a mating engage ment therebetween; and,

sealing means carried by said outlet to effect a gastight seal between said inlet and outlet when mated.

19'. In combination:

a circuit breaker tank having an opening through which servicing can be accomplished;

a support member carried by said tank within the interior thereof;

a contact and blast valve unit removably connected to said support member;

a pair of internal spaced apart rail members extending between said support-member and the opening in said tank in position to guidably support said contact and blast valveunit for movement into and out said tank, said internal rail members being disposed in a manner to direct said contact and blast valve unit as it is moved into said tank into operative engagement with said support member;

laterally extending holding means on said support memberto freely demountably receive the inboard ends of said internal rail members, the arrangement being such that said internal rails may be inserted through the opening in said tank with'the inboard ends of said rails freely engaging said laterally extending holding means for securely supporting the inboard ends of said rails;

J removable means at the opening of said tank to secure the outboard ends of said internal rail members; and,

a pair of externalspaced apart rail members extending away from the opening in. said tank, said external pair of railsbeing detachably carried by said tank in cantilever relationship,

whereby said contact and blast valve 'unit supported on the external rail members will be moved along said external rail members into said tank and on said internal rail members to be supported and guided thereby into operative association with said support member.

20. In a gas insulated circuit breaker:

an elongated circuit breaker tank;

a gas supply tank supported by said circuit breaker tank midway of the ends of said circuit breaker tank; v

a gas supply distribution member in communication with said gas supply tank and extending upwardly therefrom into said circuit tank, said gas supply distribution member having two outlets arranged to direct gas flow towards each end of said circuit breaker tank;

a contact and blast valve unit supported in operative position in one end of-said circuit breaker tank;

a gas inlet formed in said contact and blast valve unit in position to cooperatively interengage with an adjacentoutlet of said distribution member;

sealing means carried by said outlet of said distribution member to effect a gas-tight seal between said outlet and said inlet of said contact and blast valv'e unit; and, i

means operatively engaged to said other outlet of said distribution member to seal said outlet to thereby direct all gas flow from said distribution member through the outlet-associated with said contact and blast valve unit,

whereby said nonutilized outlet of said distribution member is available to receive the inlet of another contact and blast valve unit for subsequently increasing the interrupting capacity "of said circuit breaker without additional'modification of the circuit breaker. 

1. In a gas-insulated circuit breaker: a circuit breaker tank having a service opening; a contact and blast valve unit insertable through the service opening in said tank into operative position in said tank; a gas supply distribution member supported within the interior of said tank; an outlet formed on said distribution member; a tapered inlet formed in said contact and blast valve unit to cooperate with said outlet of said distribution member; and, an O-ring carried by said outlet for effecting a gas-tight seal between said outlet and inlet when mating engagement is effected between said inlet and outlet upon insertion of said contact and blast valve unit into operating position within said tank.
 2. A gas-insulated circuit breaker according to claim 1 wherein there is provided guide means to guide said contact and blast valve unit as it is inserted into operating position in said tank.
 3. In a circuit breaker: a tank; a support housing carried by said tank in the interior thereof; a contact and blast valve unit having a fastening block for securement to said support housing, said fastening block also serving as an electrical conductor between said contact and blast valve unit and said support housing; and, a conducting self-adjusting ring carried by said support member in position to be engaged by said fastening block when said contact and blast valve unit is inserted into operative position within said tank.
 4. A circuit breaker according to claim 3 wherein said fastening block is provided with a slotted opening through which fasteners are inserted to Engage in said support housing; and, capturing means associated with said fasteners and cooperable with said fastening block to retain said bolts within said slots when said fasteners are not engaged in said support housing; whereby said fasteners are readily accessible for engagement in said support housing and are prevented from accidental dislodgment from said slots when not engaged.
 5. In a circuit breaker: a tank; a support housing within said tank; a contact and blast valve unit comprising an insulator housing in which a fixed main contact is located; a main contact housing having a movable contact support projection in which a movable main contact is disposed for axial movement, said support projection extending into said insulator housing in annularly spaced relationship to thereby define an annular gas passage; an annular gas passageway formed in said main contact housing around said projection in position to communicate with the annular gas passage formed between said projection and the interior of said contact housing; a gas supply passage formed in said main contact housing in communication with said annular passage formed in said main contact housing, said gas supply passage also communicating with the end of said main contact housing; a hollow elbow secured to the end of said main contact housing and having communication with said gas supply passage, the opposite end of said elbow forming a gas inlet, the axis of which is substantially parallel to the axis of said insulator housing; a gas supply distribution member within said tank, said distribution member having an outlet which mates in sealed relationship with the inlet of said elbow; and, a valve within said elbow normally operable to seal the communication connection between said elbow and said gas supply passage in said main contact housing.
 6. In a gas-insulated circuit breaker: a circuit breaker tank having a service opening; a contact and blast valve unit insertable through the service opening in said tank into an operative position therein, said contact and blast valve unit having a gas inlet portion; a gas supply distribution means supported within said tank, said distribution means having an outlet portion complementary to said gas inlet portion of said contact and blast valve unit; and guide means operable to control the elevation of the gas inlet portion of said contact and blast valve unit to establish substantial alignment of the inlet portion relative to the complementary outlet portion of said distribution means so that mating engagement between the complementary inlet and outlet portions will occur as said contact and blast valve unit is inserted into operative position in said tank.
 7. A gas-insulated circuit breaker according to claim 6 wherein the complementary inlet and outlet portions are of annular configuration and one of said portions is provided with an annular tapered edge for facilitating the mating engagement between said portion.
 8. A gas-insulated circuit breaker according to clain 6 wherein said guide means is a ball guide supported for axial adjustment and in position to engage the bottom surface of said contact and blast valve unit as said unit is moved into operative position within the tank.
 9. A gas-insulated circuit breaker according to claim 6 wherein one of said portions carries a seal operable to seal the joint space between said complementary inlet and outlet portions when mating engagement therebetween is effected.
 10. In a gas-insulated circuit breaker: a circuit breaker tank having a service opening; a contact and blast valve unit insertable through the service opening in said tank into an operative position therein, said contact and blast valve unit having a gas inlet; a gas supply distribution member supported within said tank and having an outlet complementary to the inlet of said contact and blast valve unit for mating engagement with said outlet; and, guide means operable to control the lateral direction and the elevation of said contact and blast valve unit to establish substantial alignment of said inlet relative to said outlet so that mating engagement between said inlet and outlet will occur as said contact and blast valve unit is inserted into operating position within said tank.
 11. In combination: a circuit breaker tank having a service opening; a support member carried by said tank within the interior thereof; a contact and blast valve unit removably attached at one end to said support member; an interior rail support extending between said support member and the service opening, said interior rail support having its inner end restably confined on said support member, the outer end of said interior rail support being detachably supported by said tank at a position adjacent the service opening and at an elevation above the level at which the inner end of the rail support is supported; an exterior rail support detachably secured in cantilever relationship to said tank, said exterior rail support extending away from the opening in said tank to provide an external support for a contact and blast valve unit, said exterior rail support being in alignment with said interior rail support and having the same grade as said interior rail support; and, a breakable A-frame member having one leg releasably attached to said exterior rail support and its opposite leg releasably connected to said contact and blast valve unit; whereby collapsing of said A-frame impels said contact and blast valve unit along said rails supports and into operating engagement with said support member.
 12. In a gas circuit breaker: casing means defining an arcing chamber and having a communicating gas flow directing annular orifice portion for directing gas under pressure to said arcing chamber; a stationary contact structure having a gas exhaust opening associated therewith extending within said casing means; a movable tubular contact having a gas exhaust opening therethrough and cooperable with said stationary contact structure in said arcing chamber of said casing means; means defining a gas receiving chamber surrounding said movable contact in communication with said gas flow annular orifice portion of said casing means; a pressurized gas chamber angularly offset relative to said gas receiving chamber surrounding said movable contact and having gas under pressure therein; a gas supply passage between said pressure gas chamber and said gas receiving chamber; and, valve means in said pressurized gas chamber normally operable to seal the opening between said gas supply passage and said pressure gas chamber.
 13. A gas circuit breaker according to claim 12 wherein said casing is provided with a pocket rearwardly of the gas exhaust opening of said movable contact; and, means operable supported in said pocket out of the direct path of said gas exhaust opening of said movable contact for actuating said valve to open position to allow pressure gas to flow from said pressure gas chamber into said communicating gas supply passage.
 14. A gas circuit breaker according to claim 13 wherein there is provided operating means connected to effect synchronized opening movement of said movable contact and operation of said valve actuating means; whereby pressure gas is directed to said arcing chamber in said casing substantially at contact parting to extinguish the arc drawn between said contacts.
 15. In a gas blast circuit breaker: a circuit breaker tank; a support mounted within said tank; a contact and blast valve unit having single upper support bracket for securing said contact blast valve unit to said support housing; and, a pair of spaced apart lower securing means disposed towards the bottom of said contact and blast valve unit on each side thereof, said pair of securing means being engageable in said support housing to secure the bottOm portion of contact and blast valve unit to said support; whereby said contact and blast vlave unit is secured in operative position within said tank with three point suspension.
 16. A gas blast circuit breaker according to claim 15 wherein: said single upper support bracket is a main electrical conducting member; said support housing is provided with a self-adjusting electrical conducting washer adapted to be engaged by said upper support bracket; said spaced apart lower securing means each include an axially adjustable sleeve having a bore operatively carried by the lower portion of said contact and blast valve unit; and, a bolt extending through the axial bore in said adjustable sleeve into threaded engagement with said support housing, said bolt having abutment means engageable with said contact and blast valve unit but does not engage said sleeve, said bolts operating to secure the bottom portion of said contact and blast valve unit but does not engage said sleeve, said bolts operating to secure the bottom portion of said contact and blast valve unit to said support housing and also to lock an associated sleeve in an adjusted position; whereby each sleeve of said lower securing means can be adjusted individually to adjust the position of said contact and blat valve unit within said tank and said self-adjusting washer compensates for angular variation.
 17. In a gas blast circuit having: a tank; and, a contact and blast valve unit operatively disposed within said tank, said contact and blast valve unit comprising: a casing defining an arcing chamber and into which gas under pressure is to be supplied; a fixed tubular contact in said casing with the bore thereof operating as an exhaust passage to vent a portion of the gas supplied to said arcing chamber to said tank; a movable tubular contact supported within said arcing chamber in coaxial cooperating relationship to said fixed contact, the bore of said movable contact operating as an exhaust passage; a source of gas under pressure; a pressure gas chamber connected to receive gas under pressure from said source; an annular gas directing chamber surrounding said movable contact to direct gas under pressure to said arcing chamber, said annular gas directing chamber defining a gas exhaust passage into which the bore of said tubular movable contact vents in a straight line path; a gas flow passage in communication with said annular gas directing chamber but angularly offset therefrom, said gas flow passage also having communication with said pressure gas chamber; means normally operable to block the flow of gas under pressure from said pressure gas chamber to said gas flow passage; and, means for actuating said blocking means from its normal operating position to permit gas under pressure to escape as a blast from said pressure gas chamber into said gas flow passage, said actuating means being disposed in said gas exhaust passage defined by said annular gas directing chamber but substantially offset from the direct line of exhaust gas flow.
 18. In a gas-insulated circuit breaker: a circuit breaker tank; a gas supply tank supported by said circuit breaker tank; a gas supply distribution member in communication with said gas supply tank, said gas supply distribution member having at least one outlet; a contact and blast valve unit supported in operative position within said tank; an offset gas flow channel between said distribution member and an arcing area, the end of said offset gas flow channel adjacent said distribution member defining an inlet constructed and arranged to cooperate with the outlet presented by said distribution member, the arrangement being such that said inlet and outlet cooperate to effect a mating engagement therebetween; and, sealing means carried by said outlet to effect a gas-tight seal between said inlet and outlet when mated.
 19. In combination: a circuit breakeR tank having an opening through which servicing can be accomplished; a support member carried by said tank within the interior thereof; a contact and blast valve unit removably connected to said support member; a pair of internal spaced apart rail members extending between said support member and the opening in said tank in position to guidably support said contact and blast valve unit for movement into and out said tank, said internal rail members being disposed in a manner to direct said contact and blast valve unit as it is moved into said tank into operative engagement with said support member; laterally extending holding means on said support member to freely demountably receive the inboard ends of said internal rail members, the arrangement being such that said internal rails may be inserted through the opening in said tank with the inboard ends of said rails freely engaging said laterally extending holding means for securely supporting the inboard ends of said rails; removable means at the opening of said tank to secure the outboard ends of said internal rail members; and, a pair of external spaced apart rail members extending away from the opening in said tank, said external pair of rails being detachably carried by said tank in cantilever relationship, whereby said contact and blast valve unit supported on the external rail members will be moved along said external rail members into said tank and on said internal rail members to be supported and guided thereby into operative association with said support member.
 20. In a gas insulated circuit breaker: an elongated circuit breaker tank; a gas supply tank supported by said circuit breaker tank midway of the ends of said circuit breaker tank; a gas supply distribution member in communication with said gas supply tank and extending upwardly therefrom into said circuit tank, said gas supply distribution member having two outlets arranged to direct gas flow towards each end of said circuit breaker tank; a contact and blast valve unit supported in operative position in one end of said circuit breaker tank; a gas inlet formed in said contact and blast valve unit in position to cooperatively interengage with an adjacent outlet of said distribution member; sealing means carried by said outlet of said distribution member to effect a gas-tight seal between said outlet and said inlet of said contact and blast valve unit; and, means operatively engaged to said other outlet of said distribution member to seal said outlet to thereby direct all gas flow from said distribution member through the outlet associated with said contact and blast valve unit, whereby said nonutilized outlet of said distribution member is available to receive the inlet of another contact and blast valve unit for subsequently increasing the interrupting capacity of said circuit breaker without additional modification of the circuit breaker. 